Lubricants containing metal hydrocarbon-oxy-alkyl and hydrocarbon-oxyaryl phosphorothioate-epoxide reaction products



to the organic radicals R and R. -trated by the action of phosphorus pentasulfide on United States Patent ()flice Patented Oct. 1 2, 196 5 This invention relates as indicated to certain phosphorus thioic acid derivatives and to a process for the preparation thereof. In a more particular consideration, the invention relates to reaction products obtained from metal salts of organic phosphorus thioic acids. This application is a continuation-in-part of copending application Ser. No. 484,556 filed January 27, 1955, and now abandoned.

The products of the hereindescribed process are useful as additives for lubricants, especially for gear lubricants.

It is a principal object of the present invention to provide new compositions of matter.

It is also an object of the present invention to provide a novel process for the preparation of the above compositions of matter.

It is still a further object of the invention to provide novel additives for lubricants.

These and other objects are accomplished by a process which comprises the reaction of a metal salt of a phosphorus thioic acid having the structure PSSH where R and R' are the same or different hydrocarbonoxy-alkyl or hydrocarbon-oxy-aryl radicals, with at least about 0.5 equivalent of an organic epoxide.

The hydrocarbon-oxy-alkyl or hydrocarbon-oxyl-aryl radicals in the above structure are preferably non-functional, which is to say that they do not take part in or have any significant influence upon the reaction of the process. R and R may be aliphatic-oxy, cycloaliphaticoxy, or aromatic-oxy substituted alkyl or aryl radicals and may contain organic or inorganic substituents. Illustrative types of organic radicals include alkoxy-alkyl, cycloalkoxy-alkyl, aryl-oxy alkyl, aralkyl-oxy alkyl, alkaryl-oxy alkyl, alkenyl-oxy alkyl, cycloalkenyl-oxy, alkyl, etc., and the substituted derivatives of these; e.g., nitro-, halo-, hydroxy-, carboxy-, etc. Thus suitable organic radicals would include, e.g., methoxy-methyl, methoxy-ethyl, butoxy-propyl, butoxy-isopropyl, dodecyloxy-butyl, phenoxy-butyl, benzyl-oxy-amyl, phenethylvoxy-amyl, propylene tetramer-oxy-n-hexyl, 4-methyl-2- pentyl-oxy dodecyl, cyclohexyl-oxy-methyl, chloro-cyclohexyl-oxy-cyclohexyl, methyl cyclohexyl oxy hexyl, heptyl-oxy-octyl, n-octyl-oxy-propyl, tert-octyl-oxy-butyl, ethoxy-ethoxyl-nonyl, methoxy-propoxy-lauryl, cetyl-oxyheptyl, phen-oxy-cyclohexyl, bromophenyl-oxy-nonyl, nitro phenyl oxy hexatriacontanyl, methoxy-phenyl, ethyl-oxy-phenyl, propyl-oxy-phenyl, butyl-phenyl-oxyphenyl, amyl-phenyl-oxy-naphthyl, phenoxy-benzyl, phenethyl-oxy-phenyl, allyl oxy butyl, octenyl-oxy-phenyl, cyclohexenyl-oxy-phenyl, etc.

The phosphorodithioic acids may be prepared by the reaction of phosphorus pentasulfide with a hydrocarbonoxy-substituted hydroxy compound such as a hydrocarbon-oxy-substituted alcohol or phenol which corresponds This reaction is illusp-tert-butylphenoxy-ethyl alcohol to produce 0,0-di- (p-tert-butylphenoxy-ethyl) phosphorodithioic acid.

Metal salts of the above phosphorothioic acids may be prepared quite conveniently by treating the particular acid with a metal oxide or hydroxide. Thus, the calcium salt of a phosphorodithioic acid may be prepared from the acid by reaction with calcium oxide.

The organic epoxides may be represented as having the structural grouping where n is 0 or 1. Those epoxides are preferred in which one of the carbon atoms attached to 0 is attached also to two hydrogen atoms. In other words, the preferred compounds are terminal epoxides and have the structural grouping where n is 0 or 1. These have been given the name terminal epoxides because they may be thought of as being derived in most instances from a vinyl compound or one which has a terminal olefinic double bond.

Specific examples of suitable epoxides include ethylene oxide, propylene oxide, l-butene oxide, butadiene monoxide, l-amylene oxide, styrene oxide, trimethylene oxide, 9,10-epoxystearic acid, etc.

The reaction of organic epoxides with metal salts of phosphorothioic acids is in some cases an exothermic reaction which may be carried out conveniently within the temperature range of 0200 C. In those cases in which the reaction is exothermic, the exothermic nature of the reaction usually is such that the temperature of the reaction can be controlled within this range without the application of any external heating, by adding the organic epoxide portionwise to the salt of the phosphorothioic acid. Although it is not necessary, it is preferred to control the temperature so that it is reasonably constant throughout the course of the reaction. It is particularly preferred to control the temperature within the range of 50100 C.

The reaction may be carried out in the presence or absence of a mutual solvent for the organic epoxide and the metal salt of the phosphorothioic acid. If a solvent is used, it should be one which is inert towards both reactants such as, e.g., petroleum ether, kerosene, light and heavy mineral oils, benzene, toluene, xylene, ortho-dichlorobenzene, carbon tetrachloride, etc. Since metal salts of phosphorothioic acids are often prepared as solutions in such inert solvents, these solutions may be conveniently used for reaction with the organic epoxide.

Neither the mechanism by which the reaction proceeds nor the identity of the products which are formed thereby are known or understood. It appears that the reaction involves the addition of the epoxide to the phosphorothioic acid salt rather than a condensation of the two molecules. It appears that the preferred reaction involves equivalent amounts of the salt and epoxide, e.g., one equivalent of the metal salt of a phosphorothioic acid reacts with one equivalent amount of a terminal organic epoxide. Something more than a mere addition reaction must take place, however, since it appears that the product is not a metal salt. This is borne out by a comparison of some of its reactions with similar reactions of the corresponding metal phosphorus thioate from which it is prepared. Thus the organic portion of the metal salt which is the starting material is not affected by treatment with alcoholic hydrochloric acid, whereas in the case of its epoxide reaction product the organic portion thereof is rather completely decomposed by such treatment. In

this case it is evident that some molecular rearrangements is involved in addition to the addition of the two specified reactants. In any case, the exact molecular structure of the product is not known and for this reason the product must be described in terms of the process by which it may be prepared.

The desired products are formed by the reaction of one equivalent of the metal salt with as little as 0.5 equivalent of the epoxide. In some instances, especially where the metal salt is a Zinc salt, more than one equivalent of the epoxide may be incorporated in the metal salt. Although the upper limit of the amount of the epoxide capable of reacting with the metal salt is not known, as many as three equivalents of the epoxide may be incorporated into the product. In any event, the use of an excess amount of the epoxide has no adverse effect on the products formed and such use, therefore, is contemplated in this invention. Preferably, from about 0.5 to 1 equivalent of the epoxide is used per equivalent of the metal salt. It will be noted that the equivalent weight of the epoxide is based on the number of the epoxide radicals in a molecule and the equivalent weight of the metal phosphorothioate is based on the number of the phosphorothioic acid radicals in a molecule. For instance, the equivalent weight of propylene oxide is its molecular weight; that of a sodium phosphorothioate is its molecular weight; and that of a zinc phosphorothioate is one-half its molecular weight.

A wide variety of metal salts may be used, including both monovalent and polyvalent metal salts. The metal salts include the following: sodium, lithium, potassium, calcium, barium, strontium, magnesium, zinc, etc. The polyvalent metal salts are preferred because of the greater stability of the products obtained therefrom; and Salts of zinc and lead are especially preferred.

It should be noted that the product of the reaction of the hereindescribed process is characterized by retention of the metal in its composition. Thus, for example, the reaction product of a zinc salt of a phosphorodithioic acid and propylene oxide is characterized by the fact that it contains zinc. The zinc (or other metal, as the particular case may be) is present in the product in a relatively stable form; it cannot be washed out by aqueous washings.

Other details of the process of invention are illustrated by the following examples.

EXAMPLE 1 To 321 grams (0.5 equivalent) of zinc 0,0-di-(nonylphenoxy-ethyl) phosphorodithioate at 80 C., there is added 29 grams (0.5 equivalent) of propylene oxide. The

.propylene oxide is added at a rate sufficient to maintain To 1213 grams (0.86 equivalent) of a 46% oil solution of zinc di-(nonylphenoxyethyl) phosphorodithioate there is added at 60 65 C., 25 grams (0.43 equivalent) of propylene oxide throughout a period of 20 minutes. The mixture is heated at 6070 C. for 3 hours and then at 66 C./ 20 mm. The residue is filtered. The filtrate is a 45% oil solution of the desired product and is found to have a zinc content of 2.4%, a phosphorus content of 2.2%, and a sulfur content of 4.6%.

EXAMPLE 3 The procedure of Example 1 is repeated except that the propylene oxide used is replaced on a chemical equivalent basis with ethylene oxide.

EXAMPLE 4 The procedure of Example 2 is repeated except that the zinc di-(nonylphenoxyethyl) phosphorodithioate is replaced on a chemical equivalent basis with Zinc di-(methoxyphenyl) phosphorodithioate.

4 EXAMPLE 5 The procedure of Example 1 is repeated except that the zinc di-(nonylphenoxyethyl) phosphorodithioate is replaced on a chemical equivalent basis with zinc di-(cyclohexyloxypropyl) phosphorodithioate.

EXAMPLE 6 The procedure of Example 1 is repeated except that the zinc di-(nonylphenoxyethyl) phosphorodithioate is replaced on a chemical equivalent basis with cuprous di- (nonylphenoxyethoxyethyl) phosphorodithioate.

EXAMPLE 7 A product is obtained by the reaction at 100 C. of equivalent amounts of zinc di-(cyclohexylphenoxyethyl) phosphorodithioate and 1,2-dodecene oxide.

EXAMPLE 8 A product is obtained by the reaction at 120 C. of equivalent amounts of zinc di-(methoxyphenoxyethyl) phosphorodithioate and 1,2-octene oxide.

The metal-containing products of the process are useful as additives for lubricants. As such they impart particularly valuable properties both to motor oils and gear lubricants. The lubricating oils from which the lubricants of this invention may be prepared may be of synthetic, animal, vegetable, or mineral origin. Ordinarily mineral lubricating oils are preferred by reason of their availability, general excellence, and low'cost. For certain applications, oils belonging to one of the other groups may be preferred. For instance, synthetic polyester oils such as didodecyl adipate and di-Z-ethylhexyl sebacate are often preferred as jet engine lubricants. Normally the lubricating oils preferred will be fluid oils, ranging in viscosity from about 40 Saybolt Universal seconds at 100 F. to about 200 Saybolt Universal seconds at 210 F.

The utility of the additives of this invention is shown by the results of a test whereby their oxidation-inhibiting properties are measured. In this test, 200 grams of the test lubricant in which is immersed a copper wire (oxidation catalyst) is maintained at 300 F. for 96 hours while .air is blown through the lubricant at a rate of 25 cc./minute. At the end of the test, the increase in viscosity of the lubricant during the test period is determined and is taken as a measure of the oxidation resistance of the lubricant. The results appear in Table I.

Table 1 Test lubricant: Percent viscosity increase A. SAE mineral oil lubricant containing 0.1% of phosphorus as the product of Example 2 0.4 B. SAE 90 mineral oil lubricant containing 0.1% of phosphorus as the reaction product of zinc dihexylphosphorodithioate with 0.5 equivalent of propylene oxide 12.3

It will be noted that the product of the invention (lubricant A) is superior to the reaction product derived from a zinc dialkylphosphorodithioate (lubricant B). This difference is significant inasmuch as the latter of itself is a well-recognized lubricant additive.

The use of the hereindescribed phosphorus thioic derivatives in lubricants is further illustrated by the following specific examples:

A. SAE 90 gear lubricant 92.0 Product of Example 1 8.0 B. SAE 90 gear lubricant 96.0 Product of Example 4 4.0 C. SAE 90 gear lubricant 94.0 Product of Example 5 6.0 D. SAE 90 gear lubricant 98.0 Product of Example 6 2.0 E. SAE 90 gear lubricant 95.0

Product of Example 6 5.0

SAE 90 gear lubricant 95.3 Product of Example 7 4.7 G. SAE 90 gear lubricant 96.6 Product of Example 8 3.4 H. SAE 80 gear lubricant 90.0 Product of Example 2 10.0 I. SAE 80 gear lubricant 94.5 Product of Example 7 5.5 J. SAE 90 gear lubricant 98.0 Product of ,Example 3 2.0 K. SAE 80 gear lubricant 93.5 Product of Example 1 6.5 L. SAE 90 gear lubricant 97.5

The above gear lubricants may contain, in addition to the above specified additive, other substances which will impart desirable properties to the finished lubricant. Examples of such substances include oxidation inhibitors, extreme pressure agents, rust inhibitors, oiliness agents, etc.

To provide satisfactory protection against the ravages of extreme pressure it is desirable to incorporate into a lubricant at least about 1.0 percent of the metal-containing compositions described previously. Amounts up to 20 percent and even more are also useful. In most cases an optimum concentration is available from within the range of 3l0 percent by weight, based on the lubricating composition.

The utility of high concentration; i.e., up to 90 percent or higher, likewise is established by the convenience imparted to the problems and expense of transportation and storage. Such highly concentrated compositions, commonly termed concentrates in the trade, may then be diluted with lubricating oil at the destination point so as to provide finished lubricants containing the desired amount of metal-containing compositions of this invention.

The increase in horsepower of automotive engines has placed a corresponding increase of burden on the gear surfaces of axle units. Such a situation has enhanced to a considerable degree the utility of the hereindescribed composition. It has also pointed up the desirability and utility of combinations of various lubricant additives in which the products of this invention are useful. Such combinations as are particularly desirable include specifically the combination of any of the products of the examples herein plus a sulfur-containing organic compound which contains a sulfide linkage. The sulfide linkage contains preferably in addition to the sulfur atom(s) of the linkage, one or more sulfur atoms attached to one of these linkage sulfur atoms. Such a compound is illustrated by the structural formula Product of Example 8 where R and R are the same or different organic radicals and x is any integer, preferably from 1 to 3.

Specific examples of lubricants which contain the above combination of additives are as follows:

M. Mid-continent SAE 90 oil:

5% of the product of Example 6 2% of benzyl pentasulfide N. Mid-continent SAE 90 oil:

4% of the product of Example 7 1% of butyl tetrasulfide O. Mid-continent SAE 90 oil:

4% of the product of Example 8 1.5% of butyl tetrasulfide P. Mid-continent SAE 80 oil:

6% of the product of Example 1 3 of chlorobenzyl pentasulfide Q. Mid-continent SAE 90 oil:

10% of the product of Example 2 5% of benzyl tetrasulfide 6 R. Mid-continent SAE oil:

5.5% of the product of Example 5 2.7% of mixed benzyl tetrasulfide and pentasulfide It will be noted that the combination of ingredients (products of this invention plus polysulfides) may amount to as much as 15% by weight of the lubricant composition. Generally it is also advisable that at least 3-5% of this combination be used in an eflective gear lubricant.

A more particular definition of the amounts of ingredients which may be incorporated in the novel gear lubricants may be based on the phosphorus content and the active sulfur content which is imparted to the finished lubricant. Thus the amounts of ingredients should be such that (a) from about 0.20 to about 0.75% by weight of phosphorus, and

(b) from about 0.25 to about 1.25% by weight of active sulfur are imparted to the lubricant by these two additives.

The term active sulfur is intended to denote that portion of sulfur within a molecule which, by virtue of its mode of attachment to other atoms, has a relatively high degree of reactivity. Such sulfur can be characterized in terms of its mode of attachment in that it is thought to be attached only to other sulfur atoms. That is, a sulfur which is attached only to other sulfur atoms is said to be active sulfur whereas sulfur atoms which are bound to atoms other than sulfur are not active sulfur.

Such sulfur atoms may be said to be bonded only by secondary valence bonds.

It should be noted that where a sulfur atom is bound both to another sulfur atom and to an atom other than sulfur, such a sulfur atom is not active.

Active sulfur atoms are illustrated by (S) in each of the following structural formulae:

R-S-S-Jt It is apparent that the amount of such a compound which is used in a lubricating composition can be expressed conveniently in terms of the amount of this active sulfur. Furthermore, inasmuch as it is the active sulfur content of these compounds which characterize their performance, such a means of defining the amounts in which they may be used is particularly appropriate.

What is claimed is:

1. A lubricating composition consisting essentially of a mineral lubricating oil and from about 1% to about 20% by weight of a phosphorusand sulfur-containing material prepared by the process Which comprises the reaction of a metal salt of a phosphorus thioic acid having the structure PSSH where R and R are organic radicals selected from the class consisting of hydrocarbon-oxy-alkyl and hydrocarbon-oxy-aryl radicals, with at least about 0.5 equivalent of an epoxide selected from the class consisting of epoxy alkanes, epoxy lower alkenes, epoxy alkyl carboxylic acids, and styrene oxide at a temperature within the range of 0200 C., the metal of said metal salt being selected from the class consisting of sodium, lithium, potassium, calcium, barium, strontium, magnesium, and zinc.

2. A lubricating composition consisting essentially of a mineral lubricating oil and from about 1% to about 20% by weight of a phosphorusand sulfur-containing material prepared by the process which comprises the reaction of zinc 0,0 di (nonylphenoxy ethyl) phosphorodithioate 7 8 with one equivalent of propylene oxide at a temperature References Cited by the Examiner Within the range of 0-200 C. UNITED STATES PATENTS 3. A lubricating composition consisting essentially of 2,369,632 2/45 Cook et a1 a mineral lubricating oil and from about 1% to about 734,365 2/56 Peeso et aL y weight of a p p d r-cont 5 3,004,996 10/61 Arakelian .et a1. 25,2-.46.4 material prepared'by the process which comprises the re- FOREIGN PATENTS action of zinc di-(methoxyphenoxyethyl) phosphorodithioate with one equivalent of propylene oxide at a tem perat re w n e range of 10 DANIEL E. WYMAN, Primary Examiner.

696,064 8/53 Great Britain. 

1. A LUBRICATING COMPOSITION CONSISTING ESSENTIALLY OF A MINERAL LUBRICATING OIL AND FROM ABOUT 1% TO ABOUT 20% BY WEIGHT OF A PHOSPHORUS- AND SULFUR-CONTAINING MATERIAL PREPARED BY THE PROCESS WHICH COMPRISES THE REACTION OF METAL SALT OF A PHOSPHORUS THIOIC ACID HAVING THE STRUCTURE 